The present invention relates to a solvent separating method and apparatus of removing a solvent from a gas containing a vaporized solvent to purify the gas.
Recently, in steps of assembling and manufacturing various industrial products or household appliances or insteps of manufacturing devices which form constitutional parts of these products such as various electronic parts, various batteries or substrates, materials in a paste form having various functions are applied to devices and, then, heat treatment is performed by various heat treatment apparatuses. Here, examples of various heat treatment apparatuses include a drying furnace, a baking furnace, a curing furnace, or a reflow furnace used in soldering in an electronic part mounting step or the like. In each material in a paste form, in addition to solid components which are necessary to be contained in a final product, to apply these solid components on to various substrates or base materials, depending on various purposes and necessities, various solvents such as water or an organic solvent are mixed for viscosity adjustment or adjustment of performances.
In a heating step using a heat treatment apparatus, these solvents are discharged into the inside of the apparatus from the material in a paste form through a vaporization step and a solvent removing step. Accordingly, when heat treatment is performed continuously, the solvents are continuously vaporized and discharged into the inside of the apparatus. As a result, the concentration of the solvent in an atmosphere in the apparatus is increased, thus giving rise to a possibility that various drawbacks may take place. For example, along with the increase of solvent concentration in an atmosphere in the apparatus, an amount of solvent which can be present in the atmosphere at a temperature in the inside of the apparatus approaches a saturated state. As a result, drying of an object to be subjected to heat treatment becomes difficult. When the solvent has an explosive property, even when the solvent does not reach a saturated vapor pressure, there is a possibility that the concentration of the vaporized solvent exceeds an explosion limit. Accordingly, it is necessary to periodically or continuously supply outside air into the inside of the apparatus from the outside of the apparatus. Further, when a nitrogen gas or other atmospheres (atmospheric gases) are necessary, it is necessary to supply these atmospheres to the inside of the apparatus from the outside of the apparatus. In addition, a unit is also adapted for discharging, to the outside of the apparatus, the atmospheres in the apparatus where the solvent concentration is increased. FIG. 19 is a view for describing the supply and discharge of an atmosphere. Outside air is supplied to the inside of a heat treatment apparatus 1 by a supply blower 2. A part of atmosphere in the heat treatment apparatus 1 which contains a solvent vaporized in the inside of the heat treatment apparatus 1 is discharged to the outside of the apparatus by an exhaust blower 3. However, some solvents contained in the atmosphere and discharged to the outside of the heat treatment apparatus 1 are harmful, and there is a concern on the influence which the solvent applies to environments. In view of the above, to eliminate the influence which a solvent discharged to the outside of the heat treatment apparatus 1 and contained in a discharge atmosphere exerts on the environment such as atmospheric contamination or the influence which the solvent exerts on a health of an operator, as a method of removing a solvent from a discharge atmosphere when necessary, a method described in Patent Literature 1, for example, is known.
FIG. 20 is an explanatory view of Patent Literature 1. In this Patent Literature 1, a cooler 5 is communicated with a heat treatment apparatus 1 through a heat-treatment-apparatus inner exhaust duct 4, and a heat-treatment-apparatus outer exhaust duct 6 and a mist collector 7 are sequentially arranged in a communicating manner with the cooler 5. By cooling an exhaust atmosphere discharged from the inside of the heat treatment apparatus 1 and contains a solvent by the cooler 5, the solvent in the heat-treatment-apparatus inner atmosphere is liquefied and coagulated. Next, the atmosphere is discharged to a further downstream side through the outer exhaust duct 6 of the heat treatment apparatus, and the liquefied and coagulated solvent is collected by the mist collector 7 arranged in a communicable manner with the outer exhaust duct 6 of the heat treatment apparatus, so that the exhaust atmosphere is purified, and the purified atmosphere can be discharged to the outside of the heat treatment apparatus.
Further, as a method of removing a vaporized solvent, particularly water vapor contained in exhaust air, there has been known a method described in Patent Literature 2. FIG. 21 is an explanatory view of Patent Literature 2. The apparatus disclosed in Patent Literature 2 has the following constitution. A charge electrode 8 and an attraction electrode 9 are configured to be rotatable about a first rotary shaft 11 and a second rotary shaft 12 respectively, and the first rotary shaft 11 and the second rotary shaft 12 are connected to a drive motor 10 by way of a first drive transmission belt 13 and a second drive transmission belt 14 respectively. By driving the drive motor 10, the charge electrode 8 and the attraction electrode 9 are rotated. In such a constitution, to increase a contact area between the charge electrode 8 and the exhaust 22 and a contact area between the attraction electrode 9 and the exhaust 22, through holes 8a are formed in the charge electrode 8 and through holes 9a are formed in the attraction electrode 9. In the method disclosed in Patent Literature 2, when a solvent in the supplied exhaust 22 is vaporized, the solvent is not liquefied and coagulated through cooling. That is, a solvent vaporized on an upstream side of an exhaust flow path is charged by being brought into contact with the rotating charge electrode 8, and is moved in the direction toward the attraction electrode 9 on a downstream side of the flow path. Then, the vaporized solvent is induced by the attraction electrode 9 which has a charge of polarity opposite to polarity of a charged solvent and which rotates, and the solvent is attracted by the attraction electrode 9. The solvent attracted by the attraction electrode 9 is collected by a water droplet collector 15 due to a centrifugal force generated by the attraction electrode 9.